Bootstrap and Higher-Order Expansion Validity When Instruments May Be Weak

Marcelo J. Moreira (), Jack R. Porter and Gustavo A. Suarez

No 302, NBER Technical Working Papers from National Bureau of Economic Research, Inc

Abstract: It is well-known that size-adjustments based on Edgeworth expansions for the t-statistic perform poorly when instruments are weakly correlated with the endogenous explanatory variable. This paper shows, however, that the lack of Edgeworth expansions and bootstrap validity are not tied to the weak instrument framework, but instead depends on which test statistic is examined. In particular, Edgeworth expansions are valid for the score and conditional likelihood ratio approaches, even when the instruments are uncorrelated with the endogenous explanatory variable. Furthermore, there is a belief that the bootstrap method fails when instruments are weak, since it replaces parameters with inconsistent estimators. Contrary to this notion, we provide a theoretical proof that guarantees the validity of the bootstrap for the score test, as well as the validity of the conditional bootstrap for many conditional tests. Monte Carlo simulations show that the bootstrap actually decreases size distortions in both cases.

JEL-codes: C12 C15 C30 (search for similar items in EconPapers)
New Economics Papers: this item is included in nep-ecm
Date: Written 2004-11
Note: TWP
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